This invention relates to a method of treating biomass material such as plant biomass material, and particularly, but not exclusively, to a method of treating such materials with sufficiently large additions of the sesquioxide mineral forming constituents iron and aluminium to form protective coatings on surfaces of the material and to alter the bulk physical and chemical properties of the treated material.
The invention relates particularly to a method of treating plant material in order to protect the material from microbial decomposition.
It is known to use the reduced form of iron, Fe.sup.2+, and associated salts, in particular iron II sulphate for a number of purposes in agriculture and horticulture, including fertilisers, trace element additives, and slug and moss killers. In a particular use, Iron II sulphate has been used as an additive during the ageing and composting of wood bark, where it is used as an acidity moderator in the same way as other acidity regulating agents such as mineral sulphur.
Application of iron salts has also been used to condition mulches in order to reduce water retention.
The organic complexing properties of iron and aluminium ions in solution have been in common use in water purification treatments and the like to complex, precipitate and sediment coloured and odour producing organic species. Iron and aluminium, together with other more toxic metals such as copper, arsenic and the like are common ingredients of some types of wood preservatives used to protect wood cellulose fibres from fungal attack.
One such known application involves binding these metal ions to detergent chains.
Other wood preservative treatments use powerful iron complexing substances to ensure that fungal growth will be limited due to a shortage of available iron substances.
In a number of other known mulching and compost forming processes other means have been used for conferring protection from microbial decomposition, including resin coatings, colloidal lignite, clay minerals.
Iron III chloride has been used in the field treatment of crop residues. However, such use has proved unsatisfactory for the treatment of mulches and grain media because chloride is phytotoxic to many plant species. In addition, application of oxidised iron has been found to be ineffective at penetrating and reacting with chemical sites and internal surfaces in the treated material due to rapid precipitation.